Arc welding



Jam 7 1935- H. E. KENNEDY ET AL ARC WELDING Filed oct. 22, 1930 NQNTORS M NAR@ A. oreemu/vn.' EL Yo` y I ATTORNEYS GHiI *inherited 7, 1936 PATENT fiori-#ICE Ano WELDING Harry E. Kennedy, Maynard A. Rotermund, and Lloyd T. Jones, Berkeley, Calif., assignors to Union Carbide and Carbon Research Laboratories, Inc., a corporation of New York Application October 22, 1930, lSerial No. 490,436

14 Claims.

This invention relates to arc welding and more particularly to a welding system for automatically controlling the arc length by utilizing certain characteristics of an arc welding circuit.

It has been well established by theory and practice that in arc welding the best results are obtained when the arc is maintained uniformly short. Therefore, in continuous welding the maintenance of a constant predetermined arc length by automatically controlling the advance of the electrode material results in Welding of the highest character.

'We accomplish such an automatic control through the medium of the frequency of iiuctuations of a condition in the welding circuit which is set up by the globule movement between the electrodes. When the arc has been struck, thc electrode material becomes molten at the lower end and in obedience to the laws of capillary attraction it forms a globule which continuously increases in diameter until it becomes'of sufiicient size to contact with the material being welded. When the globule has enlarged sufficiently to bridge or short circuit the arc stream, the arc voltage decreases to practically zero and the arc current increases to short circuit value, which short circuit condition exists until the globule is no longer in contact with the electrode material.

When the electrode material is maintained in close proximity to the material being welded, the globules cannot attain a very considerable size before bridging the arc stream and short circuiting the arc. Consequently the frequency of the depositions and consequent short circuits will increase as the arc is shortened and decrease as the -arc is lengthened up to a point where the arc length is such that the globule deposits by gravity only and will not .short circuit the arc stream.

The short circuits set up by the bridging of the arc stream by the globules reflect themselves throughout the entire-welding circuit, and it is the principal object of the present invention to provide a ywelding system for automatically controlling the arc length through the medium of the frequency of the fluctuations of a condition in the 'welding circuit set up by the frequency or" metallic deposition between the electrodes.

In the accompanying drawing, the single figure diagrammatically illustrates anelectric Welding system embodying our invention.

Reference being had to the accompanying drawing, i indicates an electric motor which includes a mechanical device which grips and feeds an endless strip or" electrode material. The speed of the motor governs the movement of the electrode t0- (Cl. 21S-8) Ward the work between which and the electrode the arc is struck. Such devices are Well known inthe art and it is therefore believed unnecessary to describe its construction in detail. it will' suiiice to point out that the circuit of this motor is influenced by the arc length so as to automatically regulate the feeding of the electrode and thereby maintain a consta-nt arc length.

`The electrical circuit for operating the electrode feeding motor is connected, of course, to the armature of an' arc unit exciter or other direct current source as indicated. For iniiuencing the operation of the electrode feeding motor we have provided two circuits of different impedance receiving energy from a source or sources influenced by the arc circuit. We have found it preferable that one circuit have a high inductance and the other a high capacitance. Evidently when the frequency is low feeble current will flow in the circuit containing capacity while a strong current n0 will exist in the circuit containing inductance.

The circuits include a balanced type frequency relay l2 having a central pivotal lever` i4, oscillation of which is produced through the medium of two electromagnets i5 and i6. The magnet I6 is connected in series with an inductance across the arc stabilizing impedance, while the magnet I5 is connected in series with a condenser Il across the arc circuit. It is obvious, however, that it will be effective to reverse this order ofthe disposition of the magnets or to connect both magnet circuits either across the arc or across the stabilizing impedance. Stops I8 'limit the amount of oscillation permitted the lever i4 and the latter is connected with a damper i@ in order that it will respond to mean velues rather than individual impulses. y

In operation during the period that normal arc potential exists, the condenser circuit will pass a charging current. When the arc is short circuited by a globule bridging the arc gap, the current in this circuit will reverse and the condenser Will discharge its energy through the short circuit path provided by the globule. It will be evident from this that the mean effective current which exists in this circuit will increase with the frequency of short circuits.

The magnet IS connected as it is in series with an inductance receives a pulsating current due to the varying reactive drop which occurs across the stabilizer. This potential' will be out of phase with the potential across the arc for itis clear that during the period of yarc short circuit, a1- most the entire potential of the generator exists across the stabilizer; and conversely, when the O arc is not bridged by a globule, there is very little drop occurring across the stabilizer. This phase displacement is compensated for by the inherent characteristics of the inductance and capacity.

The mean effective voltage across the stabilizer will increase as the frequency of short circuits increases but due to the inductive nature of the circuit to which it is applied, the current will remain approximately constant. Therefore, the attraction of the magnet I6 for the lever I4 will remain substantially constant while the attraction of the magnet I5 for the lever will increase with the frequency of short circuits.

It is apparent that the relay is substantially independent of the voltage existing in thel circuit because an increase ordecrease in voltage effects both sides equally.

We may adjust the balance by means of a resistance in either operating circuit or. by an adjustable weight on the lever I4.

As shown in the drawing we utilize the relay to periodically short circuit a resistance in series with the armature of the electrode feeding motor by means of the stops or contacts I8, which are so adjusted as to open a parallel path through the resistance when the arc is short and to close the same when the arc is long. However, it is to be understood that it is within the scope of the present invention to utilize the frequency ofthe short circuits set up by the frequency of the depositions between the electrodes to influence the operation of the electrode feed motor in any other manner.

It is thus obvious that as the arc lengthens. the rate of feed of the electrode material will be increased; and as the arc decreases in length, the rate of feed of the electrode material will be decreased and so the arc length will be maintained substantially constant.

While we have disclosed one embodiment of our invention, it will be apparent that various changes may be made therein without departing from the spirit and scope ofthe invention as defined in the appended claims.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

1. In electric welding apparatus, the combination of an electrode disposed adjacent to the work and arranged to have an arc established therebetween for globules of electrode material at the arcing end of said electrode to be deposited 0n -the work, means for feeding said electrode to the work, and means operable in accordance with changes from a predetermined normal rate at which the electrode globules are depositedon the work for varying the rate of feeding of said electrode to the work.

2. In electric welding apparatus, the combination of an electrode disposed adjacent to the work and arranged to have an arc established therebetween for globules of electrode material at the arcing end of said electrode to be deposited on the work, means including an electrical device for feeding said electrode to t'he work, and means associated with said electrical device and responsive to changes from a predetermined normal rate at which the electrode globules are deposited on the work for varying the rate of feeding of said electrode to the work.

3. In electric welding apparatus, the combinationA of an electrode disposed adjacent to the work and arranged to have an arc established therebetween so that globules of electrode material formed at the arcing end of said electrode the work. 10

4. In electric welding apparatus, the combination of an electrode disposed adjacent to the work and arranged to have an arc established therebetween so that globules of electrode material formed at the arcing end of said electrode will l5 bridge the arc and be deposited on the Iwork, means including an electric motor having a circuit for feeding said electrode to the work, and control means including a condenser connected across the arc and operable in accordance with20 changes from a predetermined normal rate at which the electrode globules bridge the arc and are deposited on the work for changing a condition of said motor circuit for varying the rate of feeding of said electrode to the work.

5. In electric welding apparatus, the combination of an electrode disposed adjacent to the work and arranged to have an are established therebetween so that globules of electrode material formed at the arcing end of said electrode will 30 bridge the arc and be deposited on the work to intermittently shortcircuit the arc, means for feeding said electrode to the arc, and means associated Vwith said feeding means and connected to be effected by the intermittent short circuiting of the arc and comprising a circuit including a condenser and inductive reactance for varying the raie of feeding of said electrode tothe work with changes from a predetermined normal rate at which the electrode globules bridge the arc 40 and are deposited on the work.-

6. In welding apparatus, the combination of a welding circuit including cooperating electrodes arranged to have an arc established therebetween so that globules of electrode material formed at the end of one of said electrodes will bridge the arc gap and subsequently separate therefrom, means for feeding to the arc said electrode at which globules are formed, and meansoperable in accordance with changes in the normal predetermined rate at which the electrode globules are formed and bridge the arc gap for controlling said feeding means. 7. In Welding apparatus, the combination of a welding circuit including the work and an electrode arranged to have an arc established therebetween. said electrode and the work normally being sumciently close together for globules oi' electrode material to form at the arcing end 0f said electrode and bridge the arc gap and be de- 50 posited on the work' to cause voltage fluctuations in'said welding circuit, means including an electrical translating device for feeding said electrode to the work, and means operable in accordance with changes from a normal predetermined frequency of voltage fluctuations in said welding circuit for controlling said electrical device.

8. In welding apparatus, thecombination of a welding circuit including the work and an electrode arranged to have an arc established therebetween, said electrode and the work normally being sufliciently close together for globules of electrode material formed at the arcing end of said electrode to bridge the arc and be deposited im the work to cause voltage uctuations in said @,Gild

welding circuit, means ior feeding said electrode to the work, and means comprising a circuit including a condenser responsive to the frequency of voltage fluctuationsy in said welding circuit for controlling said feeding rneans.

9. in welding apnaratus, tire combination oi a welding circuit including the worl; and an elec trode arranged to lrave an are established there- 1cctv/een, said electrode and the work normally being suciently close together Jfor globules of electrode material iorrned at tile arcing end oi said electrode to bridge the arc and be deposited y on the work to cause voltage nuctuations in said welding circuit, means including an electrical translating device having a circuit for feeding said electrode totlie work, and means including a condenser responsive to changes in the irequency of voltage "fluctuations in said welding circuit for controlling a condition oi tne circuit of said electrical translating device.

il). 'in welding apparatus, the combination ci a welding circuit including tlle worlf; and an elec trede arranged to have an arc established therebetween so that globules of electrode material formed at the arcing end of said electrode will be deposited on the Worlr, means comprising an electrical translating device provided with a control circuit including shunt therewith for feeding said electrode to the work, and means including a condenser connected to be responsive to changes from a pre-= determined normal rate at which the electrode globules are deposited on the work for controlling said relay.

il. in welding apparatus, the combination oi l a Welding circuit including the worlr and an electrode arranged to have an arc established therebetween, said electrode and the work normally being suciently close together lor globules oi electrode material formed at tire arcing end ci said electrode to bridge tide arc and be deposited on the work to cause voltage :ductuations in said welding circuit, ineens for ieeding said electrode to the worlr, and ineens substantially indenend= ent or the average voltage in said welding circuit and operable in accordance with changes from a predetermined normal frequency of the voltage fluctuations in said welding circuit for control ling said feeding means.

'12. In welding apparatus, the combination or a welding circuit including tile work andan elec trede arranged to have an arc established there between, said electrode and the work normally a resistor having a relay in being suiilciently close together ior globules or electrode material formed at tbe arcing oZ said electrode to short circuit tne arc "ce deposited on the work to cause voltage duct sa tions in said welding circuit, means for feeding said electrode to the worlr, means operable ac= cordance with the frequency of voltage iiuctven tions in said welding circuit for controlling said feeding means, said last-mentioned means including a relay comprising a movable armature lo and a plurality or energizing coils therefor con nested to said welding circuit and arranged in opposed relation with respect to said armature, one ci said energizing coils having a condenser connected in series relation therewith.

i3. En welding apparatus, tl'le combination ci a welding circuit comprising a stabilizing imnedence and an electrode and including tire work, said electrode and the worlr being arran to have an arc established ther globules oi electrode material at the of said electrode to short circuit tine deposited on the work to cause voltiY tions in said welding circuit, said electrode to the work, means o,

ieeding means, said last-men ned means in cluding a relay comprising a movable armature and a plurality of energizing coils tliereior ar= 3@ ranged in opposed relation with respect armature, one of said coils beine connectedv across said stabilizing impedance and tlie other oi? said coils leaving a condenser in series relation tleere with and being connected across the are. 35 le. ln welding apparatus, tire combination ci an arc circuit including the worlc and a welding rod, the welding rod and the worlr normally being suciently close together so that globules o'Z welding rod material formed at the arcing end ci tire welding rod will be deposited on tile worin; electrocaliy operable rneans for feeding tire weld ing rod toward tire work; a control circuit assen elated witl'i said electrically operable ineens; means included in said control circuit and re-s ce sponsive to the rate of globular deposition or welding rod material on tine worlr for controlling said feeding ineens to maintain the rate ci denl osition of the globules substantially constantu HARRY E. KENNEDY. MAYNARU A. RTERRQUE. LLOYD 'Tl JONES. 

